What is the C# Using block and why should I use it? [duplicate]

Answer 1

If the type implements IDisposable, it automatically disposes that type.

Given:

public class SomeDisposableType : IDisposable
{
   ...implmentation details...
}

These are equivalent:

SomeDisposableType t = new SomeDisposableType();
try {
    OperateOnType(t);
}
finally {
    if (t != null) {
        ((IDisposable)t).Dispose();
    }
}

using (SomeDisposableType u = new SomeDisposableType()) {
    OperateOnType(u);
}

The second is easier to read and maintain.

Answer 2

It is really just some syntatic sugar that does not require you to explicity call Dispose on members that implement IDisposable.

Answer 3

Also take note that the object instantiated via using is read-only within the using block. Refer to the official C# reference here.

Answer 4

using (B a = new B())
{
   DoSomethingWith(a);
}

is equivalent to

B a = new B();
try
{
  DoSomethingWith(a);
}
finally
{
   ((IDisposable)a).Dispose();
}

Answer 5

From MSDN:

C#, through the .NET Framework common language runtime (CLR), automatically releases the memory used to store objects that are no longer required. The release of memory is non-deterministic; memory is released whenever the CLR decides to perform garbage collection. However, it is usually best to release limited resources such as file handles and network connections as quickly as possible.

The using statement allows the programmer to specify when objects that use resources should release them. The object provided to the using statement must implement the IDisposable interface. This interface provides the Dispose method, which should release the object's resources.

In other words, the using statement tells .NET to release the object specified in the using block once it is no longer needed.

Answer 6

The using statement obtains one or more resources, executes a statement, and then disposes of the resource.